This invention relates generally to communication systems, and more particularly to a detector for use in a receiver of multi-user communication system.
Wireless communication systems have an ever-increasing use in transferring voice and data services. Such communication systems include the Code Division Multiple Access (CDMA) standard IS-95. The CDMA system is unique in that signals from several users overlap one another in one channel simultaneously. As a result, a receiver must process the combined signal from the one channel and extract the information sent to the user of interest. This process is known as multi-user detection or joint detection. Optimal multi-user detection schemes exist, but are computationally intensive.
Various sub-optimal receiver techniques have arisen to reduce the calculations necessary to extract the original user""s signal while addressing the interference issue so as to limit error. These detection techniques include, among others, zero-forcing linear equalization, decision feedback equalization, and minimum mean-square-error equalization, used alone or in various combinations. Of these it has been reported by Klein et al. that minimum mean-square-error equalization provides the best performance in the paper xe2x80x9cZero-Forcing and Minimum Mean-Square-Error Equalization for Multiuser Detection in Code-Division Multiple-Access Channelsxe2x80x9d, IEEE Transactions on Vehicular Technology, Vol. 45, No. 2, pp. 276-287, May 1996, hereinafter referred to as MMSE-BLE (Minimum Mean Squares Error Block Linear Equalizer) useful in a CDMA system where the scrambling code is symbol-periodic.
The MMSE-BLE technique still requires extensive manipulation and calculation relating to the full system matrix defining the CDMA block transmission system channel, such as for the downlink of the proposed CDMA Third Generation Time Division Duplex (3G TDD) standard.
There is a need for improved multi-user detection in a CDMA communication system that further reduces computational complexity without sacrificing performance. It would also be of benefit to use existing hardware and to reduce processor resources.